import sequtils,strutils,math

var
    F,N,K : int
    ans : float
    fact : array[101, float]
(F, N, K) = stdin.readline.split.map(parseInt)

fact[0] = 1
for i in 1..100:
    fact[i] = i.float * fact[i - 1]

for p in 1..F:
    for j in 0..<K:
        for k in K - j..N - j:
            ans += fact[N] / fact[j] / fact[k] / fact[N - j - k] *
                pow((p - 1) / F, (N - j - k).float) * pow((F - p) /
                F, j.float) * p.float / pow(F.float, k.float)
echo ans